The present invention relates to methods for fabricating electronic devices and, more specifically, to methods for fabricating semiconductor devices.
In the course of fabricating semiconductor devices, the substrates or wafers in which the devices are made are often thinned so that the devices can meet size and performance requirements. Wafer thinning techniques, such as wafer grinding, are used to remove portions of the wafers on a side that is typically opposite to the side where the electronic circuitry is formed. The wafer surface where the thinning step is applied is often termed the “backside” of the wafer.
The wafer thinning step usually takes place towards the end of the wafer fabrication process, for example, either before a back metal step or a wafer singulation step. Prior to wafer thinning, wafers typically have a thickness of about 600 microns to about 750 microns. After the thinning step, the wafers can have a thickness of less than about 75 microns.
In a typical wafer grinding process, a protective material is placed over the front side of the wafer to protect the electronic circuitry formed thereon. The wafer is then secured to a vacuum chuck, and a rotating work chuck, which typically includes a rotating diamond cup wheel, sweeps across the wafer to remove material from the backside thereof. One problem with current wafer thinning processes is that thickness variation in the protective material can affect the final thickness uniformity or flatness of the wafer after grinding. This thickness variation can affect the reliability of the final individual semiconductor devices, resulting in increased failures.
Accordingly, it is desirable to have methods for fabricating electronic devices that improve the final thickness uniformity of thinned wafers and the individual electronic devices that are formed therein.
For simplicity and clarity of the illustration, elements in the figures are not necessarily drawn to scale, and the same reference numbers in different figures denote the same elements. Additionally, descriptions and details of well-known steps and elements are omitted for simplicity of the description.